// SPDX-License-Identifier: GPL-2.0+
/*
 * f_midi.c -- USB MIDI class function driver
 *
 * Copyright (C) 2006 Thumtronics Pty Ltd.
 * Developed for Thumtronics by Grey Innovation
 * Ben Williamson <ben.williamson@greyinnovation.com>
 *
 * Rewritten for the composite framework
 *   Copyright (C) 2011 Daniel Mack <zonque@gmail.com>
 *
 * Based on drivers/usb/gadget/f_audio.c,
 *   Copyright (C) 2008 Bryan Wu <cooloney@kernel.org>
 *   Copyright (C) 2008 Analog Devices, Inc
 *
 * and drivers/usb/gadget/midi.c,
 *   Copyright (C) 2006 Thumtronics Pty Ltd.
 *   Ben Williamson <ben.williamson@greyinnovation.com>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/device.h>
#include <linux/kfifo.h>
#include <linux/spinlock.h>

#include <sound/core.h>
#include <sound/initval.h>
#include <sound/rawmidi.h>

#include <linux/usb/ch9.h>
#include <linux/usb/func_utils.h>
#include <linux/usb/gadget.h>
#include <linux/usb/audio.h>
#include <linux/usb/midi.h>

#include "u_midi.h"

MODULE_AUTHOR("Ben Williamson");
MODULE_DESCRIPTION("USB MIDI class function driver");
MODULE_LICENSE("GPL v2");

static const char f_midi_shortname[] = "f_midi";
static const char f_midi_longname[] = "MIDI Gadget";

/*
 * We can only handle 16 cables on one single endpoint, as cable numbers are
 * stored in 4-bit fields. And as the interface currently only holds one
 * single endpoint, this is the maximum number of ports we can allow.
 */
#define MAX_PORTS 16

/* MIDI message states */
enum {
        STATE_INITIAL = 0,      /* pseudo state */
        STATE_1PARAM,
        STATE_2PARAM_1,
        STATE_2PARAM_2,
        STATE_SYSEX_0,
        STATE_SYSEX_1,
        STATE_SYSEX_2,
        STATE_REAL_TIME,
        STATE_FINISHED,         /* pseudo state */
};

/*
 * This is a gadget, and the IN/OUT naming is from the host's perspective.
 * USB -> OUT endpoint -> rawmidi
 * USB <- IN endpoint  <- rawmidi
 */
struct gmidi_in_port {
        struct snd_rawmidi_substream *substream;
        int active;
        uint8_t cable;
        uint8_t state;
        uint8_t data[2];
};

struct f_midi {
        struct usb_function     func;
        struct usb_gadget       *gadget;
        struct usb_ep           *in_ep, *out_ep;
        struct snd_card         *card;
        struct snd_rawmidi      *rmidi;
        u8                      ms_id;

        struct snd_rawmidi_substream *out_substream[MAX_PORTS];

        unsigned long           out_triggered;
        struct work_struct      work;
        unsigned int in_ports;
        unsigned int out_ports;
        int index;
        char *id;
        unsigned int buflen, qlen;
        /* This fifo is used as a buffer ring for pre-allocated IN usb_requests */
        DECLARE_KFIFO_PTR(in_req_fifo, struct usb_request *);
        spinlock_t transmit_lock;
        unsigned int in_last_port;
        unsigned char free_ref;

        struct gmidi_in_port    in_ports_array[] __counted_by(in_ports);
};

static inline struct f_midi *func_to_midi(struct usb_function *f)
{
        return container_of(f, struct f_midi, func);
}

static void f_midi_transmit(struct f_midi *midi);
static void f_midi_rmidi_free(struct snd_rawmidi *rmidi);
static void f_midi_free_inst(struct usb_function_instance *f);

DECLARE_UAC_AC_HEADER_DESCRIPTOR(1);
DECLARE_USB_MIDI_OUT_JACK_DESCRIPTOR(1);
DECLARE_USB_MS_ENDPOINT_DESCRIPTOR(16);

/* B.3.1  Standard AC Interface Descriptor */
static struct usb_interface_descriptor ac_interface_desc = {
        .bLength =              USB_DT_INTERFACE_SIZE,
        .bDescriptorType =      USB_DT_INTERFACE,
        /* .bInterfaceNumber =  DYNAMIC */
        /* .bNumEndpoints =     DYNAMIC */
        .bInterfaceClass =      USB_CLASS_AUDIO,
        .bInterfaceSubClass =   USB_SUBCLASS_AUDIOCONTROL,
        /* .iInterface =        DYNAMIC */
};

/* B.3.2  Class-Specific AC Interface Descriptor */
static struct uac1_ac_header_descriptor_1 ac_header_desc = {
        .bLength =              UAC_DT_AC_HEADER_SIZE(1),
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubtype =   USB_MS_HEADER,
        .bcdADC =               cpu_to_le16(0x0100),
        .wTotalLength =         cpu_to_le16(UAC_DT_AC_HEADER_SIZE(1)),
        .bInCollection =        1,
        /* .baInterfaceNr =     DYNAMIC */
};

/* B.4.1  Standard MS Interface Descriptor */
static struct usb_interface_descriptor ms_interface_desc = {
        .bLength =              USB_DT_INTERFACE_SIZE,
        .bDescriptorType =      USB_DT_INTERFACE,
        /* .bInterfaceNumber =  DYNAMIC */
        .bNumEndpoints =        2,
        .bInterfaceClass =      USB_CLASS_AUDIO,
        .bInterfaceSubClass =   USB_SUBCLASS_MIDISTREAMING,
        /* .iInterface =        DYNAMIC */
};

/* B.4.2  Class-Specific MS Interface Descriptor */
static struct usb_ms_header_descriptor ms_header_desc = {
        .bLength =              USB_DT_MS_HEADER_SIZE,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubtype =   USB_MS_HEADER,
        .bcdMSC =               cpu_to_le16(0x0100),
        /* .wTotalLength =      DYNAMIC */
};

/* B.5.1  Standard Bulk OUT Endpoint Descriptor */
static struct usb_endpoint_descriptor bulk_out_desc = {
        .bLength =              USB_DT_ENDPOINT_AUDIO_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bEndpointAddress =     USB_DIR_OUT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
};

static struct usb_ss_ep_comp_descriptor bulk_out_ss_comp_desc = {
        .bLength                = sizeof(bulk_out_ss_comp_desc),
        .bDescriptorType        = USB_DT_SS_ENDPOINT_COMP,
        /* .bMaxBurst           = 0, */
        /* .bmAttributes        = 0, */
};

/* B.5.2  Class-specific MS Bulk OUT Endpoint Descriptor */
static struct usb_ms_endpoint_descriptor_16 ms_out_desc = {
        /* .bLength =           DYNAMIC */
        .bDescriptorType =      USB_DT_CS_ENDPOINT,
        .bDescriptorSubtype =   USB_MS_GENERAL,
        /* .bNumEmbMIDIJack =   DYNAMIC */
        /* .baAssocJackID =     DYNAMIC */
};

/* B.6.1  Standard Bulk IN Endpoint Descriptor */
static struct usb_endpoint_descriptor bulk_in_desc = {
        .bLength =              USB_DT_ENDPOINT_AUDIO_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
};

static struct usb_ss_ep_comp_descriptor bulk_in_ss_comp_desc = {
        .bLength                = sizeof(bulk_in_ss_comp_desc),
        .bDescriptorType        = USB_DT_SS_ENDPOINT_COMP,
        /* .bMaxBurst           = 0, */
        /* .bmAttributes        = 0, */
};

/* B.6.2  Class-specific MS Bulk IN Endpoint Descriptor */
static struct usb_ms_endpoint_descriptor_16 ms_in_desc = {
        /* .bLength =           DYNAMIC */
        .bDescriptorType =      USB_DT_CS_ENDPOINT,
        .bDescriptorSubtype =   USB_MS_GENERAL,
        /* .bNumEmbMIDIJack =   DYNAMIC */
        /* .baAssocJackID =     DYNAMIC */
};

/* string IDs are assigned dynamically */

#define STRING_FUNC_IDX                 0

static struct usb_string midi_string_defs[] = {
        [STRING_FUNC_IDX].s = "MIDI function",
        {  } /* end of list */
};

static struct usb_gadget_strings midi_stringtab = {
        .language       = 0x0409,       /* en-us */
        .strings        = midi_string_defs,
};

static struct usb_gadget_strings *midi_strings[] = {
        &midi_stringtab,
        NULL,
};

static inline struct usb_request *midi_alloc_ep_req(struct usb_ep *ep,
                                                    unsigned length)
{
        return alloc_ep_req(ep, length);
}

static const uint8_t f_midi_cin_length[] = {
        0, 0, 2, 3, 3, 1, 2, 3, 3, 3, 3, 3, 2, 2, 3, 1
};

/*
 * Receives a chunk of MIDI data.
 */
static void f_midi_read_data(struct usb_ep *ep, int cable,
                             uint8_t *data, int length)
{
        struct f_midi *midi = ep->driver_data;
        struct snd_rawmidi_substream *substream = midi->out_substream[cable];

        if (!substream)
                /* Nobody is listening - throw it on the floor. */
                return;

        if (!test_bit(cable, &midi->out_triggered))
                return;

        snd_rawmidi_receive(substream, data, length);
}

static void f_midi_handle_out_data(struct usb_ep *ep, struct usb_request *req)
{
        unsigned int i;
        u8 *buf = req->buf;

        for (i = 0; i + 3 < req->actual; i += 4)
                if (buf[i] != 0) {
                        int cable = buf[i] >> 4;
                        int length = f_midi_cin_length[buf[i] & 0x0f];
                        f_midi_read_data(ep, cable, &buf[i + 1], length);
                }
}

static void
f_midi_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct f_midi *midi = ep->driver_data;
        struct usb_composite_dev *cdev = midi->func.config->cdev;
        int status = req->status;

        switch (status) {
        case 0:                  /* normal completion */
                if (ep == midi->out_ep) {
                        /* We received stuff. req is queued again, below */
                        f_midi_handle_out_data(ep, req);
                } else if (ep == midi->in_ep) {
                        /* Our transmit completed. See if there's more to go.
                         * f_midi_transmit eats req, don't queue it again. */
                        req->length = 0;
                        queue_work(system_highpri_wq, &midi->work);
                        return;
                }
                break;

        /* this endpoint is normally active while we're configured */
        case -ECONNABORTED:     /* hardware forced ep reset */
        case -ECONNRESET:       /* request dequeued */
        case -ESHUTDOWN:        /* disconnect from host */
                VDBG(cdev, "%s gone (%d), %d/%d\n", ep->name, status,
                                req->actual, req->length);
                if (ep == midi->out_ep) {
                        f_midi_handle_out_data(ep, req);
                        /* We don't need to free IN requests because it's handled
                         * by the midi->in_req_fifo. */
                        free_ep_req(ep, req);
                }
                return;

        case -EOVERFLOW:        /* buffer overrun on read means that
                                 * we didn't provide a big enough buffer.
                                 */
        default:
                DBG(cdev, "%s complete --> %d, %d/%d\n", ep->name,
                                status, req->actual, req->length);
                break;
        case -EREMOTEIO:        /* short read */
                break;
        }

        status = usb_ep_queue(ep, req, GFP_ATOMIC);
        if (status) {
                ERROR(cdev, "kill %s:  resubmit %d bytes --> %d\n",
                                ep->name, req->length, status);
                usb_ep_set_halt(ep);
                /* FIXME recover later ... somehow */
        }
}

static void f_midi_drop_out_substreams(struct f_midi *midi)
{
        unsigned int i;

        for (i = 0; i < midi->in_ports; i++) {
                struct gmidi_in_port *port = midi->in_ports_array + i;
                struct snd_rawmidi_substream *substream = port->substream;

                if (port->active && substream)
                        snd_rawmidi_drop_output(substream);
        }
}

static int f_midi_start_ep(struct f_midi *midi,
                           struct usb_function *f,
                           struct usb_ep *ep)
{
        int err;
        struct usb_composite_dev *cdev = f->config->cdev;

        usb_ep_disable(ep);

        err = config_ep_by_speed(midi->gadget, f, ep);
        if (err) {
                ERROR(cdev, "can't configure %s: %d\n", ep->name, err);
                return err;
        }

        err = usb_ep_enable(ep);
        if (err) {
                ERROR(cdev, "can't start %s: %d\n", ep->name, err);
                return err;
        }

        ep->driver_data = midi;

        return 0;
}

static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
        struct f_midi *midi = func_to_midi(f);
        unsigned i;
        int err;

        /* we only set alt for MIDIStreaming interface */
        if (intf != midi->ms_id)
                return 0;

        err = f_midi_start_ep(midi, f, midi->in_ep);
        if (err)
                return err;

        err = f_midi_start_ep(midi, f, midi->out_ep);
        if (err)
                return err;

        /* pre-allocate write usb requests to use on f_midi_transmit. */
        while (kfifo_avail(&midi->in_req_fifo)) {
                struct usb_request *req =
                        midi_alloc_ep_req(midi->in_ep, midi->buflen);

                if (req == NULL)
                        return -ENOMEM;

                req->length = 0;
                req->complete = f_midi_complete;

                kfifo_put(&midi->in_req_fifo, req);
        }

        /* allocate a bunch of read buffers and queue them all at once. */
        for (i = 0; i < midi->qlen && err == 0; i++) {
                struct usb_request *req =
                        midi_alloc_ep_req(midi->out_ep, midi->buflen);

                if (req == NULL)
                        return -ENOMEM;

                req->complete = f_midi_complete;
                err = usb_ep_queue(midi->out_ep, req, GFP_ATOMIC);
                if (err) {
                        ERROR(midi, "%s: couldn't enqueue request: %d\n",
                                    midi->out_ep->name, err);
                        if (req->buf != NULL)
                                free_ep_req(midi->out_ep, req);
                        return err;
                }
        }

        return 0;
}

static void f_midi_disable(struct usb_function *f)
{
        struct f_midi *midi = func_to_midi(f);
        struct usb_composite_dev *cdev = f->config->cdev;
        struct usb_request *req = NULL;

        DBG(cdev, "disable\n");

        /*
         * just disable endpoints, forcing completion of pending i/o.
         * all our completion handlers free their requests in this case.
         */
        usb_ep_disable(midi->in_ep);
        usb_ep_disable(midi->out_ep);

        /* release IN requests */
        while (kfifo_get(&midi->in_req_fifo, &req))
                free_ep_req(midi->in_ep, req);

        f_midi_drop_out_substreams(midi);
}

static int f_midi_snd_free(struct snd_device *device)
{
        return 0;
}

/*
 * Converts MIDI commands to USB MIDI packets.
 */
static void f_midi_transmit_byte(struct usb_request *req,
                                 struct gmidi_in_port *port, uint8_t b)
{
        uint8_t p[4] = { port->cable << 4, 0, 0, 0 };
        uint8_t next_state = STATE_INITIAL;

        switch (b) {
        case 0xf8 ... 0xff:
                /* System Real-Time Messages */
                p[0] |= 0x0f;
                p[1] = b;
                next_state = port->state;
                port->state = STATE_REAL_TIME;
                break;

        case 0xf7:
                /* End of SysEx */
                switch (port->state) {
                case STATE_SYSEX_0:
                        p[0] |= 0x05;
                        p[1] = 0xf7;
                        next_state = STATE_FINISHED;
                        break;
                case STATE_SYSEX_1:
                        p[0] |= 0x06;
                        p[1] = port->data[0];
                        p[2] = 0xf7;
                        next_state = STATE_FINISHED;
                        break;
                case STATE_SYSEX_2:
                        p[0] |= 0x07;
                        p[1] = port->data[0];
                        p[2] = port->data[1];
                        p[3] = 0xf7;
                        next_state = STATE_FINISHED;
                        break;
                default:
                        /* Ignore byte */
                        next_state = port->state;
                        port->state = STATE_INITIAL;
                }
                break;

        case 0xf0 ... 0xf6:
                /* System Common Messages */
                port->data[0] = port->data[1] = 0;
                port->state = STATE_INITIAL;
                switch (b) {
                case 0xf0:
                        port->data[0] = b;
                        port->data[1] = 0;
                        next_state = STATE_SYSEX_1;
                        break;
                case 0xf1:
                case 0xf3:
                        port->data[0] = b;
                        next_state = STATE_1PARAM;
                        break;
                case 0xf2:
                        port->data[0] = b;
                        next_state = STATE_2PARAM_1;
                        break;
                case 0xf4:
                case 0xf5:
                        next_state = STATE_INITIAL;
                        break;
                case 0xf6:
                        p[0] |= 0x05;
                        p[1] = 0xf6;
                        next_state = STATE_FINISHED;
                        break;
                }
                break;

        case 0x80 ... 0xef:
                /*
                 * Channel Voice Messages, Channel Mode Messages
                 * and Control Change Messages.
                 */
                port->data[0] = b;
                port->data[1] = 0;
                port->state = STATE_INITIAL;
                if (b >= 0xc0 && b <= 0xdf)
                        next_state = STATE_1PARAM;
                else
                        next_state = STATE_2PARAM_1;
                break;

        case 0x00 ... 0x7f:
                /* Message parameters */
                switch (port->state) {
                case STATE_1PARAM:
                        if (port->data[0] < 0xf0)
                                p[0] |= port->data[0] >> 4;
                        else
                                p[0] |= 0x02;

                        p[1] = port->data[0];
                        p[2] = b;
                        /* This is to allow Running State Messages */
                        next_state = STATE_1PARAM;
                        break;
                case STATE_2PARAM_1:
                        port->data[1] = b;
                        next_state = STATE_2PARAM_2;
                        break;
                case STATE_2PARAM_2:
                        if (port->data[0] < 0xf0)
                                p[0] |= port->data[0] >> 4;
                        else
                                p[0] |= 0x03;

                        p[1] = port->data[0];
                        p[2] = port->data[1];
                        p[3] = b;
                        /* This is to allow Running State Messages */
                        next_state = STATE_2PARAM_1;
                        break;
                case STATE_SYSEX_0:
                        port->data[0] = b;
                        next_state = STATE_SYSEX_1;
                        break;
                case STATE_SYSEX_1:
                        port->data[1] = b;
                        next_state = STATE_SYSEX_2;
                        break;
                case STATE_SYSEX_2:
                        p[0] |= 0x04;
                        p[1] = port->data[0];
                        p[2] = port->data[1];
                        p[3] = b;
                        next_state = STATE_SYSEX_0;
                        break;
                }
                break;
        }

        /* States where we have to write into the USB request */
        if (next_state == STATE_FINISHED ||
            port->state == STATE_SYSEX_2 ||
            port->state == STATE_1PARAM ||
            port->state == STATE_2PARAM_2 ||
            port->state == STATE_REAL_TIME) {

                unsigned int length = req->length;
                u8 *buf = (u8 *)req->buf + length;

                memcpy(buf, p, sizeof(p));
                req->length = length + sizeof(p);

                if (next_state == STATE_FINISHED) {
                        next_state = STATE_INITIAL;
                        port->data[0] = port->data[1] = 0;
                }
        }

        port->state = next_state;
}

static int f_midi_do_transmit(struct f_midi *midi, struct usb_ep *ep)
{
        struct usb_request *req = NULL;
        unsigned int len, i;
        bool active = false;
        int err;

        /*
         * We peek the request in order to reuse it if it fails to enqueue on
         * its endpoint
         */
        len = kfifo_peek(&midi->in_req_fifo, &req);
        if (len != 1) {
                ERROR(midi, "%s: Couldn't get usb request\n", __func__);
                return -1;
        }

        /*
         * If buffer overrun, then we ignore this transmission.
         * IMPORTANT: This will cause the user-space rawmidi device to block
         * until a) usb requests have been completed or b) snd_rawmidi_write()
         * times out.
         */
        if (req->length > 0)
                return 0;

        for (i = midi->in_last_port; i < midi->in_ports; ++i) {
                struct gmidi_in_port *port = midi->in_ports_array + i;
                struct snd_rawmidi_substream *substream = port->substream;

                if (!port->active || !substream)
                        continue;

                while (req->length + 3 < midi->buflen) {
                        uint8_t b;

                        if (snd_rawmidi_transmit(substream, &b, 1) != 1) {
                                port->active = 0;
                                break;
                        }
                        f_midi_transmit_byte(req, port, b);
                }

                active = !!port->active;
                if (active)
                        break;
        }
        midi->in_last_port = active ? i : 0;

        if (req->length <= 0)
                goto done;

        err = usb_ep_queue(ep, req, GFP_ATOMIC);
        if (err < 0) {
                ERROR(midi, "%s failed to queue req: %d\n",
                      midi->in_ep->name, err);
                req->length = 0; /* Re-use request next time. */
        } else {
                /* Upon success, put request at the back of the queue. */
                kfifo_skip(&midi->in_req_fifo);
                kfifo_put(&midi->in_req_fifo, req);
        }

done:
        return active;
}

static void f_midi_transmit(struct f_midi *midi)
{
        struct usb_ep *ep = midi->in_ep;
        int ret;
        unsigned long flags;

        /* We only care about USB requests if IN endpoint is enabled */
        if (!ep || !ep->enabled)
                goto drop_out;

        spin_lock_irqsave(&midi->transmit_lock, flags);

        do {
                ret = f_midi_do_transmit(midi, ep);
                if (ret < 0) {
                        spin_unlock_irqrestore(&midi->transmit_lock, flags);
                        goto drop_out;
                }
        } while (ret);

        spin_unlock_irqrestore(&midi->transmit_lock, flags);

        return;

drop_out:
        f_midi_drop_out_substreams(midi);
}

static void f_midi_in_work(struct work_struct *work)
{
        struct f_midi *midi;

        midi = container_of(work, struct f_midi, work);
        f_midi_transmit(midi);
}

static int f_midi_in_open(struct snd_rawmidi_substream *substream)
{
        struct f_midi *midi = substream->rmidi->private_data;
        struct gmidi_in_port *port;

        if (substream->number >= midi->in_ports)
                return -EINVAL;

        VDBG(midi, "%s()\n", __func__);
        port = midi->in_ports_array + substream->number;
        port->substream = substream;
        port->state = STATE_INITIAL;
        return 0;
}

static int f_midi_in_close(struct snd_rawmidi_substream *substream)
{
        struct f_midi *midi = substream->rmidi->private_data;

        VDBG(midi, "%s()\n", __func__);
        return 0;
}

static void f_midi_in_trigger(struct snd_rawmidi_substream *substream, int up)
{
        struct f_midi *midi = substream->rmidi->private_data;

        if (substream->number >= midi->in_ports)
                return;

        VDBG(midi, "%s() %d\n", __func__, up);
        midi->in_ports_array[substream->number].active = up;
        if (up)
                queue_work(system_highpri_wq, &midi->work);
}

static int f_midi_out_open(struct snd_rawmidi_substream *substream)
{
        struct f_midi *midi = substream->rmidi->private_data;

        if (substream->number >= MAX_PORTS)
                return -EINVAL;

        VDBG(midi, "%s()\n", __func__);
        midi->out_substream[substream->number] = substream;
        return 0;
}

static int f_midi_out_close(struct snd_rawmidi_substream *substream)
{
        struct f_midi *midi = substream->rmidi->private_data;

        VDBG(midi, "%s()\n", __func__);
        return 0;
}

static void f_midi_out_trigger(struct snd_rawmidi_substream *substream, int up)
{
        struct f_midi *midi = substream->rmidi->private_data;

        VDBG(midi, "%s()\n", __func__);

        if (up)
                set_bit(substream->number, &midi->out_triggered);
        else
                clear_bit(substream->number, &midi->out_triggered);
}

static const struct snd_rawmidi_ops gmidi_in_ops = {
        .open = f_midi_in_open,
        .close = f_midi_in_close,
        .trigger = f_midi_in_trigger,
};

static const struct snd_rawmidi_ops gmidi_out_ops = {
        .open = f_midi_out_open,
        .close = f_midi_out_close,
        .trigger = f_midi_out_trigger
};

static inline void f_midi_unregister_card(struct f_midi *midi)
{
        if (midi->card) {
                snd_card_free(midi->card);
                midi->card = NULL;
        }
}

/* register as a sound "card" */
static int f_midi_register_card(struct f_midi *midi)
{
        struct snd_card *card;
        struct snd_rawmidi *rmidi;
        int err;
        static struct snd_device_ops ops = {
                .dev_free = f_midi_snd_free,
        };

        err = snd_card_new(&midi->gadget->dev, midi->index, midi->id,
                           THIS_MODULE, 0, &card);
        if (err < 0) {
                ERROR(midi, "snd_card_new() failed\n");
                goto fail;
        }
        midi->card = card;

        err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, midi, &ops);
        if (err < 0) {
                ERROR(midi, "snd_device_new() failed: error %d\n", err);
                goto fail;
        }

        strscpy(card->driver, f_midi_longname);
        strscpy(card->longname, f_midi_longname);
        strscpy(card->shortname, f_midi_shortname);

        /* Set up rawmidi */
        snd_component_add(card, "MIDI");
        err = snd_rawmidi_new(card, card->longname, 0,
                              midi->out_ports, midi->in_ports, &rmidi);
        if (err < 0) {
                ERROR(midi, "snd_rawmidi_new() failed: error %d\n", err);
                goto fail;
        }
        midi->rmidi = rmidi;
        midi->in_last_port = 0;
        strscpy(rmidi->name, card->shortname);
        rmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT |
                            SNDRV_RAWMIDI_INFO_INPUT |
                            SNDRV_RAWMIDI_INFO_DUPLEX;
        rmidi->private_data = midi;
        rmidi->private_free = f_midi_rmidi_free;
        midi->free_ref++;

        /*
         * Yes, rawmidi OUTPUT = USB IN, and rawmidi INPUT = USB OUT.
         * It's an upside-down world being a gadget.
         */
        snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, &gmidi_in_ops);
        snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT, &gmidi_out_ops);

        /* register it - we're ready to go */
        err = snd_card_register(card);
        if (err < 0) {
                ERROR(midi, "snd_card_register() failed\n");
                goto fail;
        }

        VDBG(midi, "%s() finished ok\n", __func__);
        return 0;

fail:
        f_midi_unregister_card(midi);
        return err;
}

/* MIDI function driver setup/binding */

static int f_midi_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct usb_descriptor_header **midi_function;
        struct usb_midi_in_jack_descriptor jack_in_ext_desc[MAX_PORTS];
        struct usb_midi_in_jack_descriptor jack_in_emb_desc[MAX_PORTS];
        struct usb_midi_out_jack_descriptor_1 jack_out_ext_desc[MAX_PORTS];
        struct usb_midi_out_jack_descriptor_1 jack_out_emb_desc[MAX_PORTS];
        struct usb_composite_dev *cdev = c->cdev;
        struct f_midi *midi = func_to_midi(f);
        struct usb_string *us;
        struct f_midi_opts *opts;
        int status, n, jack = 1, i = 0, endpoint_descriptor_index = 0;

        midi->gadget = cdev->gadget;
        INIT_WORK(&midi->work, f_midi_in_work);
        status = f_midi_register_card(midi);
        if (status < 0)
                goto fail_register;

        opts = container_of(f->fi, struct f_midi_opts, func_inst);
        if (opts->interface_string)
                midi_string_defs[STRING_FUNC_IDX].s = opts->interface_string;

        /* maybe allocate device-global string ID */
        us = usb_gstrings_attach(c->cdev, midi_strings,
                                 ARRAY_SIZE(midi_string_defs));
        if (IS_ERR(us)) {
                status = PTR_ERR(us);
                goto fail;
        }
        ac_interface_desc.iInterface = us[STRING_FUNC_IDX].id;

        /* We have two interfaces, AudioControl and MIDIStreaming */
        status = usb_interface_id(c, f);
        if (status < 0)
                goto fail;
        ac_interface_desc.bInterfaceNumber = status;

        status = usb_interface_id(c, f);
        if (status < 0)
                goto fail;
        ms_interface_desc.bInterfaceNumber = status;
        ac_header_desc.baInterfaceNr[0] = status;
        midi->ms_id = status;

        status = -ENODEV;

        /*
         * Reset wMaxPacketSize with maximum packet size of FS bulk transfer before
         * endpoint claim. This ensures that the wMaxPacketSize does not exceed the
         * limit during bind retries where configured dwc3 TX/RX FIFO's maxpacket
         * size of 512 bytes for IN/OUT endpoints in support HS speed only.
         */
        bulk_in_desc.wMaxPacketSize = cpu_to_le16(64);
        bulk_out_desc.wMaxPacketSize = cpu_to_le16(64);

        /* allocate instance-specific endpoints */
        midi->in_ep = usb_ep_autoconfig(cdev->gadget, &bulk_in_desc);
        if (!midi->in_ep)
                goto fail;

        midi->out_ep = usb_ep_autoconfig(cdev->gadget, &bulk_out_desc);
        if (!midi->out_ep)
                goto fail;

        /* allocate temporary function list */
        midi_function = kzalloc_objs(*midi_function, (MAX_PORTS * 4) + 11);
        if (!midi_function) {
                status = -ENOMEM;
                goto fail;
        }

        /*
         * construct the function's descriptor set. As the number of
         * input and output MIDI ports is configurable, we have to do
         * it that way.
         */

        /* add the headers - these are always the same */
        midi_function[i++] = (struct usb_descriptor_header *) &ac_interface_desc;
        midi_function[i++] = (struct usb_descriptor_header *) &ac_header_desc;
        midi_function[i++] = (struct usb_descriptor_header *) &ms_interface_desc;

        /* calculate the header's wTotalLength */
        n = USB_DT_MS_HEADER_SIZE
                + (midi->in_ports + midi->out_ports) *
                        (USB_DT_MIDI_IN_SIZE + USB_DT_MIDI_OUT_SIZE(1));
        ms_header_desc.wTotalLength = cpu_to_le16(n);

        midi_function[i++] = (struct usb_descriptor_header *) &ms_header_desc;

        /* configure the external IN jacks, each linked to an embedded OUT jack */
        for (n = 0; n < midi->in_ports; n++) {
                struct usb_midi_in_jack_descriptor *in_ext = &jack_in_ext_desc[n];
                struct usb_midi_out_jack_descriptor_1 *out_emb = &jack_out_emb_desc[n];

                in_ext->bLength                 = USB_DT_MIDI_IN_SIZE;
                in_ext->bDescriptorType         = USB_DT_CS_INTERFACE;
                in_ext->bDescriptorSubtype      = USB_MS_MIDI_IN_JACK;
                in_ext->bJackType               = USB_MS_EXTERNAL;
                in_ext->bJackID                 = jack++;
                in_ext->iJack                   = 0;
                midi_function[i++] = (struct usb_descriptor_header *) in_ext;

                out_emb->bLength                = USB_DT_MIDI_OUT_SIZE(1);
                out_emb->bDescriptorType        = USB_DT_CS_INTERFACE;
                out_emb->bDescriptorSubtype     = USB_MS_MIDI_OUT_JACK;
                out_emb->bJackType              = USB_MS_EMBEDDED;
                out_emb->bJackID                = jack++;
                out_emb->bNrInputPins           = 1;
                out_emb->pins[0].baSourcePin    = 1;
                out_emb->pins[0].baSourceID     = in_ext->bJackID;
                out_emb->iJack                  = 0;
                midi_function[i++] = (struct usb_descriptor_header *) out_emb;

                /* link it to the endpoint */
                ms_in_desc.baAssocJackID[n] = out_emb->bJackID;
        }

        /* configure the external OUT jacks, each linked to an embedded IN jack */
        for (n = 0; n < midi->out_ports; n++) {
                struct usb_midi_in_jack_descriptor *in_emb = &jack_in_emb_desc[n];
                struct usb_midi_out_jack_descriptor_1 *out_ext = &jack_out_ext_desc[n];

                in_emb->bLength                 = USB_DT_MIDI_IN_SIZE;
                in_emb->bDescriptorType         = USB_DT_CS_INTERFACE;
                in_emb->bDescriptorSubtype      = USB_MS_MIDI_IN_JACK;
                in_emb->bJackType               = USB_MS_EMBEDDED;
                in_emb->bJackID                 = jack++;
                in_emb->iJack                   = 0;
                midi_function[i++] = (struct usb_descriptor_header *) in_emb;

                out_ext->bLength =              USB_DT_MIDI_OUT_SIZE(1);
                out_ext->bDescriptorType =      USB_DT_CS_INTERFACE;
                out_ext->bDescriptorSubtype =   USB_MS_MIDI_OUT_JACK;
                out_ext->bJackType =            USB_MS_EXTERNAL;
                out_ext->bJackID =              jack++;
                out_ext->bNrInputPins =         1;
                out_ext->iJack =                0;
                out_ext->pins[0].baSourceID =   in_emb->bJackID;
                out_ext->pins[0].baSourcePin =  1;
                midi_function[i++] = (struct usb_descriptor_header *) out_ext;

                /* link it to the endpoint */
                ms_out_desc.baAssocJackID[n] = in_emb->bJackID;
        }

        /* configure the endpoint descriptors ... */
        ms_out_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->out_ports);
        ms_out_desc.bNumEmbMIDIJack = midi->out_ports;

        ms_in_desc.bLength = USB_DT_MS_ENDPOINT_SIZE(midi->in_ports);
        ms_in_desc.bNumEmbMIDIJack = midi->in_ports;

        /* ... and add them to the list */
        endpoint_descriptor_index = i;
        midi_function[i++] = (struct usb_descriptor_header *) &bulk_out_desc;
        midi_function[i++] = (struct usb_descriptor_header *) &ms_out_desc;
        midi_function[i++] = (struct usb_descriptor_header *) &bulk_in_desc;
        midi_function[i++] = (struct usb_descriptor_header *) &ms_in_desc;
        midi_function[i++] = NULL;

        /*
         * support all relevant hardware speeds... we expect that when
         * hardware is dual speed, all bulk-capable endpoints work at
         * both speeds
         */
        /* copy descriptors, and track endpoint copies */
        f->fs_descriptors = usb_copy_descriptors(midi_function);
        if (!f->fs_descriptors)
                goto fail_f_midi;

        bulk_in_desc.wMaxPacketSize = cpu_to_le16(512);
        bulk_out_desc.wMaxPacketSize = cpu_to_le16(512);
        f->hs_descriptors = usb_copy_descriptors(midi_function);
        if (!f->hs_descriptors)
                goto fail_f_midi;

        bulk_in_desc.wMaxPacketSize = cpu_to_le16(1024);
        bulk_out_desc.wMaxPacketSize = cpu_to_le16(1024);
        i = endpoint_descriptor_index;
        midi_function[i++] = (struct usb_descriptor_header *)
                             &bulk_out_desc;
        midi_function[i++] = (struct usb_descriptor_header *)
                             &bulk_out_ss_comp_desc;
        midi_function[i++] = (struct usb_descriptor_header *)
                             &ms_out_desc;
        midi_function[i++] = (struct usb_descriptor_header *)
                             &bulk_in_desc;
        midi_function[i++] = (struct usb_descriptor_header *)
                             &bulk_in_ss_comp_desc;
        midi_function[i++] = (struct usb_descriptor_header *)
                             &ms_in_desc;
        f->ss_descriptors = usb_copy_descriptors(midi_function);
        if (!f->ss_descriptors)
                goto fail_f_midi;

        kfree(midi_function);

        return 0;

fail_f_midi:
        kfree(midi_function);
        usb_free_all_descriptors(f);
fail:
        f_midi_unregister_card(midi);
fail_register:
        ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);

        return status;
}

static inline struct f_midi_opts *to_f_midi_opts(struct config_item *item)
{
        return container_of(to_config_group(item), struct f_midi_opts,
                            func_inst.group);
}

static void midi_attr_release(struct config_item *item)
{
        struct f_midi_opts *opts = to_f_midi_opts(item);

        usb_put_function_instance(&opts->func_inst);
}

static const struct configfs_item_operations midi_item_ops = {
        .release        = midi_attr_release,
};

#define F_MIDI_OPT(name, test_limit, limit)                             \
static ssize_t f_midi_opts_##name##_show(struct config_item *item, char *page) \
{                                                                       \
        struct f_midi_opts *opts = to_f_midi_opts(item);                \
        int result;                                                     \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        result = sprintf(page, "%u\n", opts->name);                     \
        mutex_unlock(&opts->lock);                                      \
                                                                        \
        return result;                                                  \
}                                                                       \
                                                                        \
static ssize_t f_midi_opts_##name##_store(struct config_item *item,     \
                                         const char *page, size_t len)  \
{                                                                       \
        struct f_midi_opts *opts = to_f_midi_opts(item);                \
        int ret;                                                        \
        u32 num;                                                        \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        if (opts->refcnt > 1) {                                         \
                ret = -EBUSY;                                           \
                goto end;                                               \
        }                                                               \
                                                                        \
        ret = kstrtou32(page, 0, &num);                                 \
        if (ret)                                                        \
                goto end;                                               \
                                                                        \
        if (test_limit && num > limit) {                                \
                ret = -EINVAL;                                          \
                goto end;                                               \
        }                                                               \
        opts->name = num;                                               \
        ret = len;                                                      \
                                                                        \
end:                                                                    \
        mutex_unlock(&opts->lock);                                      \
        return ret;                                                     \
}                                                                       \
                                                                        \
CONFIGFS_ATTR(f_midi_opts_, name);

#define F_MIDI_OPT_SIGNED(name, test_limit, limit)                              \
static ssize_t f_midi_opts_##name##_show(struct config_item *item, char *page) \
{                                                                       \
        struct f_midi_opts *opts = to_f_midi_opts(item);                \
        int result;                                                     \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        result = sprintf(page, "%d\n", opts->name);                     \
        mutex_unlock(&opts->lock);                                      \
                                                                        \
        return result;                                                  \
}                                                                       \
                                                                        \
static ssize_t f_midi_opts_##name##_store(struct config_item *item,     \
                                         const char *page, size_t len)  \
{                                                                       \
        struct f_midi_opts *opts = to_f_midi_opts(item);                \
        int ret;                                                        \
        s32 num;                                                        \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        if (opts->refcnt > 1) {                                         \
                ret = -EBUSY;                                           \
                goto end;                                               \
        }                                                               \
                                                                        \
        ret = kstrtos32(page, 0, &num);                                 \
        if (ret)                                                        \
                goto end;                                               \
                                                                        \
        if (test_limit && num > limit) {                                \
                ret = -EINVAL;                                          \
                goto end;                                               \
        }                                                               \
        opts->name = num;                                               \
        ret = len;                                                      \
                                                                        \
end:                                                                    \
        mutex_unlock(&opts->lock);                                      \
        return ret;                                                     \
}                                                                       \
                                                                        \
CONFIGFS_ATTR(f_midi_opts_, name);

#define F_MIDI_OPT_STRING(name)                                         \
static ssize_t f_midi_opts_##name##_show(struct config_item *item, char *page) \
{                                                                       \
        struct f_midi_opts *opts = to_f_midi_opts(item);                \
        ssize_t result;                                                 \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        if (opts->name) {                                               \
                result = strscpy(page, opts->name, PAGE_SIZE);          \
        } else {                                                        \
                page[0] = 0;                                            \
                result = 0;                                             \
        }                                                               \
                                                                        \
        mutex_unlock(&opts->lock);                                      \
                                                                        \
        return result;                                                  \
}                                                                       \
                                                                        \
static ssize_t f_midi_opts_##name##_store(struct config_item *item,     \
                                         const char *page, size_t len)  \
{                                                                       \
        struct f_midi_opts *opts = to_f_midi_opts(item);                \
        int ret;                                                        \
        char *c;                                                        \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        if (opts->refcnt > 1) {                                         \
                ret = -EBUSY;                                           \
                goto end;                                               \
        }                                                               \
                                                                        \
        c = kstrndup(page, len, GFP_KERNEL);                            \
        if (!c) {                                                       \
                ret = -ENOMEM;                                          \
                goto end;                                               \
        }                                                               \
        kfree(opts->name);                                              \
        opts->name = c;                                                 \
        ret = len;                                                      \
end:                                                                    \
        mutex_unlock(&opts->lock);                                      \
        return ret;                                                     \
}                                                                       \
                                                                        \
CONFIGFS_ATTR(f_midi_opts_, name)

F_MIDI_OPT_SIGNED(index, true, SNDRV_CARDS);
F_MIDI_OPT(buflen, false, 0);
F_MIDI_OPT(qlen, false, 0);
F_MIDI_OPT(in_ports, true, MAX_PORTS);
F_MIDI_OPT(out_ports, true, MAX_PORTS);
F_MIDI_OPT_STRING(id);
F_MIDI_OPT_STRING(interface_string);

static struct configfs_attribute *midi_attrs[] = {
        &f_midi_opts_attr_index,
        &f_midi_opts_attr_buflen,
        &f_midi_opts_attr_qlen,
        &f_midi_opts_attr_in_ports,
        &f_midi_opts_attr_out_ports,
        &f_midi_opts_attr_id,
        &f_midi_opts_attr_interface_string,
        NULL,
};

static const struct config_item_type midi_func_type = {
        .ct_item_ops    = &midi_item_ops,
        .ct_attrs       = midi_attrs,
        .ct_owner       = THIS_MODULE,
};

static void f_midi_free_inst(struct usb_function_instance *f)
{
        struct f_midi_opts *opts;
        bool free = false;

        opts = container_of(f, struct f_midi_opts, func_inst);

        mutex_lock(&opts->lock);
        if (!--opts->refcnt) {
                free = true;
        }
        mutex_unlock(&opts->lock);

        if (free) {
                kfree(opts->id);
                kfree(opts->interface_string);
                kfree(opts);
        }
}

static struct usb_function_instance *f_midi_alloc_inst(void)
{
        struct f_midi_opts *opts;

        opts = kzalloc_obj(*opts);
        if (!opts)
                return ERR_PTR(-ENOMEM);

        mutex_init(&opts->lock);
        opts->func_inst.free_func_inst = f_midi_free_inst;
        opts->index = SNDRV_DEFAULT_IDX1;
        opts->id = NULL;
        opts->interface_string = NULL;
        opts->buflen = 512;
        opts->qlen = 32;
        opts->in_ports = 1;
        opts->out_ports = 1;
        opts->refcnt = 1;

        config_group_init_type_name(&opts->func_inst.group, "",
                                    &midi_func_type);

        return &opts->func_inst;
}

static void f_midi_free(struct usb_function *f)
{
        struct f_midi *midi;
        struct f_midi_opts *opts;
        bool free = false;

        midi = func_to_midi(f);
        opts = container_of(f->fi, struct f_midi_opts, func_inst);
        mutex_lock(&opts->lock);
        if (!--midi->free_ref) {
                kfree(midi->id);
                kfifo_free(&midi->in_req_fifo);
                kfree(midi);
                free = true;
        }
        mutex_unlock(&opts->lock);

        if (free)
                f_midi_free_inst(&opts->func_inst);
}

static void f_midi_rmidi_free(struct snd_rawmidi *rmidi)
{
        f_midi_free(rmidi->private_data);
}

static void f_midi_unbind(struct usb_configuration *c, struct usb_function *f)
{
        struct usb_composite_dev *cdev = f->config->cdev;
        struct f_midi *midi = func_to_midi(f);
        struct snd_card *card;

        DBG(cdev, "unbind\n");

        /* just to be sure */
        f_midi_disable(f);

        card = midi->card;
        midi->card = NULL;
        if (card)
                snd_card_free_when_closed(card);

        usb_free_all_descriptors(f);
}

static struct usb_function *f_midi_alloc(struct usb_function_instance *fi)
{
        struct f_midi *midi = NULL;
        struct f_midi_opts *opts;
        int status, i;

        opts = container_of(fi, struct f_midi_opts, func_inst);

        mutex_lock(&opts->lock);
        /* sanity check */
        if (opts->in_ports > MAX_PORTS || opts->out_ports > MAX_PORTS) {
                status = -EINVAL;
                goto setup_fail;
        }

        /* allocate and initialize one new instance */
        midi = kzalloc_flex(*midi, in_ports_array, opts->in_ports);
        if (!midi) {
                status = -ENOMEM;
                goto setup_fail;
        }
        midi->in_ports = opts->in_ports;

        for (i = 0; i < opts->in_ports; i++)
                midi->in_ports_array[i].cable = i;

        /* set up ALSA midi devices */
        midi->id = kstrdup(opts->id, GFP_KERNEL);
        if (opts->id && !midi->id) {
                status = -ENOMEM;
                goto midi_free;
        }
        midi->out_ports = opts->out_ports;
        midi->index = opts->index;
        midi->buflen = opts->buflen;
        midi->qlen = opts->qlen;
        midi->in_last_port = 0;
        midi->free_ref = 1;

        status = kfifo_alloc(&midi->in_req_fifo, midi->qlen, GFP_KERNEL);
        if (status)
                goto midi_free;

        spin_lock_init(&midi->transmit_lock);

        ++opts->refcnt;
        mutex_unlock(&opts->lock);

        midi->func.name         = "gmidi function";
        midi->func.bind         = f_midi_bind;
        midi->func.unbind       = f_midi_unbind;
        midi->func.set_alt      = f_midi_set_alt;
        midi->func.disable      = f_midi_disable;
        midi->func.free_func    = f_midi_free;

        return &midi->func;

midi_free:
        if (midi)
                kfree(midi->id);
        kfree(midi);
setup_fail:
        mutex_unlock(&opts->lock);

        return ERR_PTR(status);
}

DECLARE_USB_FUNCTION_INIT(midi, f_midi_alloc_inst, f_midi_alloc);